Control System, Automatic Transmission
Automatic transmissions AF20 (2.0i) and AF22 (2.3i and 2.6i) are electronically-controlled 4-speed automatic transmissions which are fitted together with different engine variants.
The transmission is controlled by a Transmission Control Module (TCM), which is fed with digital and analogue signals. The TCM uses this information to control the transmission's hydraulic system by means of electronic control signals.
Compared with the conventional hydraulically-controlled transmissions the AF20 and AF22 have the following advantages:
^ Improved quality and softer gear-shifting, as the torque is reduced during gear-shifting
^ Lower fuel consumption because of a driving program which is designed to optimize the consumption
^ The possibility to select various driving programs: NORMAL, SPORT, WINTER
^ Reduced mechanical stresses on the entire transmission
^ Self-diagnosis and storing of diagnostic trouble codes
LIMP-HOME MODE
If a fault should occur in the transmission control module or in any of the sensors, the system goes into an emergency operation program, the limp-home mode. It is then only possible to run the car in 3, 4 and R gears by moving the selector lever manually between these positions.
The emergency operation program gives a gear position as follows:
Gear position P R N D 3 2 1
Emergency operation P R N 4 4 3 3
ELECTRONIC REVERSE GEAR LOCK
When you shift to R from D, 3, 2 or 1 at the same time as the car exceeds a certain speed, the transmission control module sends a signal to solenoid S1, which prevents the reverse gear from being engaged (brake B3 releases).
The electronic reverse gear lock is released when:
1. The speed of the car falls below 7 km/h (4 mph).
2. The selector lever is moved to a position other than R.
ELECTRONIC OVER-REVVING PROTECTOR
To prevent the engine from over-revving, the transmission is fitted with an over-revving protector. This means that it is not possible to shift to a lower gear until the speed of the car is below the limit value for the gear in question.
4-3 177
3-2 116
2-1 65
SHIFTING OF GEAR N - D AND N - R
Shifting of Gear N-D
When you move the selector lever from N to D, the transmission goes temporarily into third gear in order to make the gear shifting as smooth as possible. This compensation is carried out on condition that:
1. The brake light switch is activated
2. The throttle is closed
3. Shifting takes place from N to D
4. The speed of the car is below 5 km/h
5. Selected gear shift program is NORMAL or SPORT
Shifting of Gear N-D and N-R
When the selector lever is moved to 1, 2, 3 or D from P, R or N, or to R from other positions, the TCM sends a signal to the engine control module which lowers the ignition and thus reduces the engine's torque to reduce any jerks when shifting gear.
The condition for this to happen is that the opening of the throttle is >20%.
TCM
The TCM controls the operation of the transmission by deciding on the basis of a certain amount of information how the hydraulic system should be affected.
The information is obtained from a number of sensors and by communication with other systems in the car.
When the information has been processed, the TCM controls the shifting of gears, the lock-up function and the system pressure using 4 solenoids. Gear shifting is carried out using shift solenoids S1 and S2, the lock-up function by the torque converter clutch (TCC) solenoid (solenoid SL) and the system pressure by the pressure control solenoid ST.
CONTROL OF THE LOCK-UP FUNCTION
The lock-up function is controlled by the TCM switching the TCC solenoid on/off depending on the speed of the car and the opening of the throttle.
In the following cases the lock-up function is disconnected:
^ if an electrical fault occurs, so that limp-home is activated
^ when the brake light switch is activated and the input speed to the transmission is <2000 rpm
^ when the accelerator pedal is disengaged and the speed of the car is <125 km/h (78 mph) and the selector lever is in position D
CONTROL OF THE SYSTEM PRESSURE
The system pressure can be varied by the TCM switching on/off the pressure control solenoid.
When shifting gear N - R, the TCM lowers the system pressure with the help of the solenoid, in order to reduce any jerks from the shifting of gears.
When the fluid temperature is <10°C and the speed of the car is <5 km/h (3 mph) the TCM increases the system pressure with the help of the solenoid, in order to reduce the time taken to shift gears.
The function is disengaged in the following situations:
^ fluid temperature >20°C
^ speed of car >7 km/h (4 mph)
^ a change in the position of the selector lever
ELECTRONIC FAULT-TRACING
The TCM is also connected to the car's data link connector, which means that it is possible to carry out fault-tracing with ISAT.
TCM POWER SUPPLY
Battery Voltage +30
The TCM is continuously powered by battery voltage +30 on pin 18.
The TCM uses this voltage to maintain power to the memory. Power supply in stand-by position is less than 1 mA.
Battery Voltage +15
When the ignition key is in drive position the TCM receives +15 voltage on pin 17. The voltage is necessary to activate the system.
Grounding Points
The ground connections to pins 22 and 35 are internally connected in the TCM and are, electrically, the same point. The ground points have been duplicated in order to increase safety and functionality.
With the ignition in drive position it is possible to check the TCM's grounding points with the help of a voltmeter by measuring the voltage between pin 22 and the battery's negative terminal and between pin 35 and the battery's positive terminal.
In both cases the voltage should be less than 0.1 V
INPUTS TO THE TRANSMISSION CONTROL MODULE (TCM)
^ Input shaft speed sensor, incoming rpm (pins 12, 31)
^ Output shaft speed sensor, outgoing rpm (pins 30, 31)
^ Transmission fluid temperature sensor (pin 33)
^ Transmission range switch (pins 9,10, 27, 28)
^ Throttle position (pin 25)
^ Throttle Position (TPS) (pin 15)
^ Traction Control System (TCS) ACTIVE (pin 4)
^ Brake light switch (pin 26)
^ Data link K line (pin 23) (also output)
^ SPORT switch (pin 20)
^ WINTER switch (pin 21)
^ Kick-down switch (pin 8)
^ Shift-lock relay (pins 10,28)
^ Voltage from +15 (pin 17)
^ Voltage from +30 (pin 18), Ground (pins 22, 35)
OUTPUTS OF THE TRANSMISSION CONTROL MODULE (TCM)
^ Shift solenoid S1 (pin 1)
^ Shift solenoid S2 (pin 3)
^ Torque converter clutch (TCC) solenoid SL (pin 19)
^ Pressure control solenoid (pins 16, 34)
^ SPORT indicator lamp (pin 24)
^ WINTER-indicator lamp (pin 7)
^ Warning lamp CHECK GEARBOX (pin 6)
^ Signal, torque limitation (pin 13)
^ Signal, drive (pin 11)
^ Data link K (pin 23) (also input)
INPUT SHAFT SPEED SENSOR
The Input Shaft Speed (ISS) sensor is fitted in the transmission housing. It gives the TCM information about the incoming rpm to the transmission.
The ISS sensor is of the electro-magnetic (inductive) type and measures the incoming rpm after the torque converter (the turbine rpm) by being affected by a toothed pulse wheel (a drum on the C1 clutch). The sensor's signal voltage, a sine voltage, increases with the engine speed. When idling it is 1.2 - 1.4 V and at 2500 rpm it is 2.2 V, measured between pins 2 and 1 on the sensor.
Pin 12 is signal voltage and pin 31 is signal ground. The resistance between pins 2 and 1 on the sensor connector is 300 - 600 ohms.
The TCM uses the ISS rpm signal and the speed of the car to calculate gear shifting times. The information about rpm and speed affects the regulation of fluid pressure, control of the lock-up function and the reduction in torque, which results in smooth shifting of gears.
OUTPUT SHAFT SPEED SENSOR
The Output Shaft Speed (OSS) sensor is fitted in the transmission housing. It gives the TCM information about the outgoing rpm of the transmission. The OSS sensor is of the electro-magnetic (inductive) type and measures the outgoing rpm by being affected by a toothed pulse wheel (the parking lock's ring gear). The sensor's signal voltage, a sine voltage, increases with the speed of the car. At 30 km/h it is about 1.1 V and 110Hz measured between pins 30 and 31 on the sensor.
Pin 30 is signal voltage and pin 31 is signal ground. The resistance between pins 3 and 2 on the sensor connector is 300 - 600 ohms.
The TCM uses the speed signal to check the points of time of the gear shiftings.
TRANSMISSION FLUID TEMPERATURE SENSOR
The transmission fluid temperature sensor, which is fitted in the transmission housing, gives the TCM information about the current transmission fluid temperature.
The sensor is of the NTC type, i e the sensor's built-in resistance has a negative temperature dependence: the resistance is reduced when the temperature rises. This property means that the voltage level varies on TCM input pin 33.
The variations in resistance and voltage are shown in the table below.
The sensor is grounded in ground point G34S, car body ground.
The TCM uses the temperature information to calculate gear shifting points and when to connect the lock-up function.
Oil temp Resistance Voltage, pin 33
°C (Ohms) ±10% (V) ±10%
-10 5000 4.6
0 2000 4.1
+20 900 3.4
+40 400 2.4
+80 125 1.1
+100 75 0.7
+150 27 0.3
TRANSMISSION RANGE SWITCH, GEAR ENGAGED
The Transmission Range (TR) switch is fitted on the transmission housing. It contains the reversing light switch, starting interlock contact and switches which inform the TCM about which range (gear) the transmission is operating in.
In principle, the TR switch is a position switch which is powered via +X and in which a number of slip contacts indicate the position. The combination of terminals A, B, C and D gives the selector lever position (see table above). The slip contacts can be either closed (=ON) or open (=OFF).
TRANSMISSION RANGE SWITCH - REVERSING LIGHT CONTACT
Contact function 31 pins 1 and 2 is used to control the reversing light.
When gear position R is selected, the contact is closed and there is power to the reversing light lamps. In other gear positions the contact is open.
In markets with side reversing lights this contact controls the reversing light relay (405), which feeds power to all reversing light lamps.
STARTING INTERLOCK CONTACT
Contact function 77 pin 5/7 is used to control the starting relay.
Contact pin 7 is powered via fuse 36 with battery positive voltage. In cars with an anti-theft alarm the power supply comes via this alarm control module. In the P and N positions contact function 77 is closed and the battery positive voltage is fed to the starting relay.
In all other gear positions the contact function is open, i.e. the starting relay receives no voltage.
THROTTLE POSITION
The MOTRONIC SFI system contains a throttle position sensor which gives information about the opening angle of the throttle. The MOTRONIC ECM distributes a throttle position signal to other systems, like for example the automatic transmission.
The TCM receives the throttle position signal on pin 25 from pin 52 on Motronic 2.10.2. The signal is a 100 Hz PWM signal, in which the pulse ratio indicates the opening angle of the throttle. The pulse ratio varies from 9% at idling to 92% at wide open throttle.
The TCM uses the throttle position signal to control gear shifting points and the system pressure.
BRAKE LIGHT SWITCH
The brake light switch gives information to the TCM and the shift-lock relay.
When the brake pedal is applied, the brake light switch is activated and sends information to the TCM on pin 26, which results in the lock-up being disengaged. The activation results in battery positive voltage on pin 26.
On markets with a shift-lock function there is a circuit for the shift-lock relay and its electro-magnet. The selector lever is in position P during starting and can only be moved when the brake has been activated. When the brake pedal is engaged, this is registered by the brake light switch which controls the electro-magnet via pin 87 on the shift-lock relay.
DATA LINK K LINE
The Transmission Control Module's (TCM) communication with the ISAT scan tool is via pin 23.
The communication on data the link K line flows in both directions and thus constitutes both input and output signals.
The data link connector is situated under the facia on the driver's side.
With the ignition in drive position the voltage on pin 23 is 9 - 11 V when ISAT is connected.